Here at The Nature Nook, we just love frogs and toads. We think they are fantastic – and, in many cases, a little freaky. After all, there are frogs out there that raise their tadpoles in their vocal sacs. Frogs that can survive being frozen solid. A frog that was used as an early pregnancy test. A toad whose young erupt from their mother’s back. In this new regular feature, we’ll be looking at all of these freaky frogs – and many more.
Today, however, we’ll be easing ourselves into the world of frogs and toads with a brief introduction. They are all members of the order Anura, which literally means ‘without tail’ because they are the only amphibians to lack them as adults. Frogs and toads are also the most numerous amphibians in the world, with over 7,200 species, accounting for over 88% of all living amphibian species.
But, before we get ahead of ourselves, a question that many people ask:
What is the Difference Between a Frog and a Toad?
Perhaps surprisingly, the answer to that question is ‘not much’. In fact, there is no real scientific difference between the two. All species in the order Anura can accurately be called frogs. A ‘toad’ is simply a type of frog that usually – but not always – spends most of its time on land rather than in water. In consequence, these species tend to have dry, warty skin and shorter hind legs that are more suited for walking than jumping or swimming.
In Britain, this distinction makes a degree of sense, for there are only two native species of frog – the common frog (seen in the image at the top of the page) and the pool frog – both of which live predominantly in water; and two native species of toad – the common toad and the much rarer natterjack toad – which tend to live on land and have warty skin.
But when you consider the group as a whole, across the entire world, this rule does not necessarily hold up, so a species can often be called either a frog or toad with equal accuracy. Many ‘toads’ have frog-like characteristics and vice versa. The Surinam toad, for example, spends almost its entire life in water and yet it is still called a toad. The reason for this is primarily down to aesthetics. When particularly unattractive species were first discovered, they were often called toads – and the Surinam toad is undeniably very ugly indeed (but that’s a story for another time). The only family of anurans in which all members are known as toads is Bufonidae (bufo is Latin for ‘toad’).
Little and Large
The largest species of frog (or anuran, if you wish) is the goliath frog, which lives only in a small area of fast-flowing rivers in the rainforest of Cameroon and Equatorial Guinea in West Africa. It can measure 34 cm from snout to vent (60 cm if you include the legs) and weigh up to 3 kg – about the same size as the world’s smallest antelope. Its large, powerful legs enable this oversized amphibian to jump forward almost 3 metres.
The goliath frog eats mainly invertebrates such as dragonflies and spiders, but it is quite capable of taking down smaller amphibians, baby turtles, and young snakes. You might think that such a large frog would make a particularly loud croak, but this species has no vocal sac and doesn’t make much noise beyond a whistling sound used by the male to attract a mate. The frog’s near-silence makes it difficult to find, despite its size, which means that relatively little is known about it. We do know, however, that the restricted distribution of the goliath frog makes it vulnerable to habitat loss, collection for the pet trade, and harvesting by humans for food. Indeed, in its native range, the meat of this bulky frog is highly prized and considered a delicacy.
At the other end of the anuran size scale is a species that is roughly 40 times smaller than the goliath frog. This tiny species doesn’t even have a common name – it is known only as Paedophryne amauensis. Averaging just 7.7mm in length – about the size of a baked bean – it is not only the smallest frog in the world, but it’s also the smallest known vertebrate, beating the previous record-holder, a minuscule goby from Australia.
Because of its diminutive size, Paedophryne amanuensis was only officially described in 2012. Even then, it was only discovered when scientists used triangulation to locate the source of this frog’s peeping, insect-like call. It inhabits the moist leaf litter on the forest floor in New Guinea, hunting minuscule invertebrates. Unusually, it lives its entire life on land and doesn’t even have a tadpole stage.
Next time, we’ll really start delving into the world of freaky frogs. First up – the Lake Titicaca frog, whose excessive, baggy skin has given it the delightful nickname of ‘scrotum frog’.